Apparatus and method for reducing three-dimensional visual fatigue

1. An apparatus reducing three-dimensional (3D) visual fatigue, the apparatus comprising: a viewing distance estimator to determine a user-to-screen distance from a screen to a user; a 3D image analyzer to calculate a user-to-3D object distance based on the determined user-to-screen distance and a parallax of a 3D image; a 3D visual fatigue predictor to predict 3D visual fatigue of the user based on the determined user-to-screen distance and the calculated user-to-3D object distance; and a 3D image controller to control the 3D image based on the predicted 3D visual fatigue, wherein the 3D visual fatigue predictor comprises: a 3D visual fatigue model-based predictor to predict 3D visual fatigue based on a 3D visual fatigue model using the calculated user-to-3D object distance and determined user-to-screen distance, wherein the 3D visual fatigue model comprises 3D visual fatigue information regarding at least one user-to-screen distance and at least one user-to-3D object distance; a fatigue-causing determiner to determine whether the 3D visual fatigue model indicates an occurrence of 3D visual fatigue based on the predicted 3D visual fatigue, wherein the fatigue-causing determiner determines an occurrence of 3D visual fatigue if the predicted 3D visual fatigue is equal to or greater than a predetermined reference value; and an optimal user-to-3D object distance calculator to calculate an optimal user-to-3D object distance using the determined user-to-screen distance and at least one user-to-3D object distance from the 3D visual fatigue model, when the predicted 3D visual fatigue is equal to or greater than the predetermined reference value.

2. The apparatus of claim 1 , wherein the 3D image analyzer comprises: a pixel disparity calculator to read a first 3D image and a second 3D image from the 3D image, and to calculate a pixel disparity between the first 3D image and the second 3D image; a physical disparity calculator to reflect a width and a horizontal resolution of the screen on the calculated pixel disparity, and to calculate a physical disparity; and a user-to-3D object distance calculator to calculate the user-to-3D object distance based on the calculated pixel disparity and the calculated physical disparity.

3. The apparatus of claim 2 , wherein the user-to-3D object distance calculator calculates the user-to-3D object distance based on the calculated pixel disparity, the calculated physical disparity, and a distance between eyes of the user.

4. The apparatus of claim 1 , wherein the viewing distance estimator comprises: a viewing distance measuring unit to measure the user-to-screen distance; and a viewing distance calculator to calculate the user-to-screen distance based on the measured distance.

5. The apparatus of claim 1 , wherein the viewing distance estimator determines the user-to-screen distance using at least one of a monocular camera, a stereo camera, a multi-camera, a depth measurement camera, an ultrasonic distance measurement sensor, an infrared distance measurement sensor, and a laser distance measurement sensor.

6. The apparatus of claim 1 , wherein the 3D visual fatigue predictor comprises: a 3D visual fatigue model storage unit to store the 3D visual fatigue model, the 3D visual fatigue model comprising the 3D visual fatigue information regarding at least one user-to-screen distance and at least one 3D viewing distance.

7. The apparatus of claim 6 , wherein the 3D visual fatigue model is stored in a storage.

8. The apparatus of claim 7 , wherein the stored 3D visual fatigue model is stored in a form of a lookup table or an approximated function.

9. The apparatus of claim 1 , wherein the 3D image controller comprises: an optimal physical disparity calculator to calculate an optimal physical disparity based on the calculated optimal user-to-3D object distance obtained using the determined user-to-screen distance and at least one user-to-3D object distance from the 3D visual fatigue model; an optimal pixel disparity calculator to calculate an optimal pixel disparity based on the calculated optimal physical disparity; and an optimal 3D image regenerator to regenerate a 3D image based on the calculated optimal physical disparity and the calculated optimal pixel disparity.

10. The apparatus of claim 1 , further comprising: a 3D image display unit to display a 3D image.

11. A method of reducing three-dimensional (3D) visual fatigue, the method comprising: determining a user-to-screen distance from a screen to a user; calculating a user-to-3D object distance based on the determined user-to-screen distance and a parallax of a 3D image; predicting 3D visual fatigue of the user based on the determined user-to-screen distance and the calculated user-to-3D object distance; and controlling the 3D image based on the predicted 3D visual fatigue, wherein the predicting comprises: predicting 3D visual fatigue based on a 3D visual fatigue model using the calculated user-to-3D object distance and determined user-to-screen distance, wherein the 3D visual fatigue model comprises 3D visual fatigue information regarding at least one user-to-screen distance and at least one user-to-3D object distance; determining whether the 3D visual fatigue model indicates an occurrence of 3D visual fatigue by determining based on the predicted 3D visual fatigue, wherein an occurrence of 3D visual fatigue is determined if the predicted 3D visual fatigue is equal to or greater than a predetermined reference value; and calculating an optimal user-to-3D object distance using the determined user-to-screen distance and at least one user-to-3D object distance from the 3D visual fatigue model, when the predicted 3D visual fatigue is equal to or greater than the predetermined reference value.

12. The method of claim 11 , wherein the calculating comprises: reading a first 3D image and a second 3D image from the 3D image, and calculating a pixel disparity between the first 3D image and the second 3D image; reflecting a width and a horizontal resolution of the screen on the calculated pixel disparity, and calculating a physical disparity; and calculating the user-to-3D object distance based on the calculated pixel disparity and the calculated physical disparity.

13. A non-transitory computer-readable medium to store computer-readable instructions, that when executed, performs the method of: determining a user-to-screen distance from a screen to a user; calculating a user-to-3D object distance based on the determined user-to-screen distance and a parallax of a 3D image; predicting 3D visual fatigue of the user based on the determined user-to-screen distance and the calculated user-to-3D object distance; and controlling the 3D image based on the predicted 3D visual fatigue, wherein the predicting comprises: predicting 3D visual fatigue based on a 3D visual fatigue model using the calculated user-to-3D object distance and determined user-to-screen distance, wherein the 3D visual fatigue model comprises 3D visual fatigue information regarding at least one user-to-screen distance and at least one user-to-3D object distance; determining whether the 3D visual fatigue model indicates an occurrence of 3D visual fatigue by determining based on the predicted 3D visual fatigue, wherein an occurrence of 3D visual fatigue is determined if the predicted 3D visual fatigue is equal to or greater than a predetermined reference value; and calculating an optimal user-to-3D object distance using the determined user-to-screen distance and at least one user-to-3D object distance from the 3D visual fatigue model, when the predicted 3D visual fatigue is equal to or greater than the predetermined reference value.